iv PREFACE. 



strongly affect our conceptions of the underlying principles 

 of such correlated sciences as sociology, pedagogy, etc. It 

 is, then, as a means of orientation in evolutionary matters for 

 the general reader and for the unspecialised but interested 

 student of science that this book is prepared. 



That it may not be without some special usefulness to 

 more advanced students and biological workers there are 

 added, in appendices to the chapters, special notes (referred 

 to in the text by small super-numbers) in which are given 

 numerous exact references to general or special books or 

 papers, and accounts, in more or less detail, of particular 

 observations, experiments, or theoretical discussions, as well 

 as references to extended bibliographic lists of the subjects 

 under treatment. These notes will enable students, or others 

 interested, to look up the original sources of our knowledge 

 of the subjects of the various chapters, and to find more 

 detailed general or special discussions of them than can be 

 given in this book. These notes also enable the author to 

 introduce into the book some details of his own observations 

 and experiments touching various evolutionary subjects. 



V. L. K. 



STANFORD UNIVERSITY, June, 1907. 



